British journal of anaesthesia
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Behavioural pain tools are used in Intensive Care Unit (ICU) patients unable to self-report their pain-intensity but need sustained efforts to educate and train the ICU team because of the subjective nature of these clinical tools. This study measured the validity and performance of an electrophysiological monitoring tool based on the spectral analysis of heart rate variability, the Analgesia Nociception Index (ANI) which varies from 0 (minimal parasympathetic tone, maximal stress-response and pain) to 100 (maximal parasympathetic tone, minimal stress-response and pain). ⋯ Despite low sensitivity/specificity, ANIi≥43 had a Negative-Predictive-Value of 90%. Hence ANIi may be of highest benefit for excluding significant pain. A randomized controlled trial should compare sedation-analgesia protocols based on ANIi to presently recommended behavioural-pain-tools.
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Actions of general anaesthetics on activity in the cortico-thalamic network likely contribute to loss of consciousness and disconnection from the environment. Previously, we showed that the general anaesthetic isoflurane preferentially suppresses cortically evoked synaptic responses compared with thalamically evoked synaptic responses, but how this differential sensitivity translates into changes in network activity is unclear. ⋯ Disruption of horizontal activity spread and of layer 1 facilitation of thalamo-cortical responses likely contribute to the mechanism by which suppression of cortical feedback connections disrupts sensory awareness under anaesthesia.
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We used functional connectivity measures from brain resting state functional magnetic resonance imaging to identify human neural correlates of sedation with dexmedetomidine or propofol and their similarities with natural sleep. ⋯ Thalamic connectivity with key nodes of arousal and saliency detection networks was relatively preserved during N3 sleep and dexmedetomidine-induced unresponsiveness as compared to propofol. These network effects may explain the rapid recovery of oriented responsiveness to external stimulation seen under dexmedetomidine sedation.